The present invention relates to a method and apparatus for the circular and/or spiral winding of composite flexible material and more specifically, to the formation of a cylindrical body such as for a container from a treated blank, in a preferred embodiment, or which may be in continuous flexible sheet form.
In this field, devices have been employed to spirally wind ribbons of web-like material, often with the application of an adhesive, around a stationary mandrel with no more than two belt pulled around the mandrel and running at an angle to the axis of the mandrel. The web material is fed longitudinally between the mandrel surface and the belt or belts and pulled down the mandrel due to the relative rotation of the belt on a spiral path with respect to the axis of the mandrel. With this type of procedure, a continuous cylinder is formed which may be subsequently severed transverse to its axis to form discrete cylindrical containers. While this arrangement has been useful, it suffers from the disadvantage that it is relatively unstable due to the number of variables which adversely affect the control over the quality of the product produced.
In a method described as convolute, an adhesive is applied to portions of one or more sheets of flexible material and then the material is wound around a rotating mandrel along a feed direction that is at 90.degree. to the axis of the mandrel. After the winding is completed, the formed cylinder is stripped from the mandrel for any additional process handling. The next sheet or sheets are then wrapped as the first sheet.
An apparatus and process similar to the foregoing is described in U.S. Pat. No. 3,252,388 where an adehsive coated blank is fed to a roll member where the adhesive is cured. The roll member is enclosed in a tube which serves to guide the blank into a cylindrical shape.
Apart from the difficulties associated with feeding an adhesive coated blank into a cylindrical path, this arrangement suffers from the obvious disadvantage that the sheet material must be completely formed into a cylinder on the roll or mandrel and moved off the mandrel before the next article can be processed.
In another arrangement, the blank forming of cylinder bodies from sheet material involves the steps of bringing a single sheet up and around a mandrel so that the adjacent edges of the blank align and overlap which are then bonded together in the area of overlap. This process is, of course, time consuming and labor intensive.
The present invention overcomes the foregoing disadvantages and provides substantially enhanced efficiency in forming either spirally wound cylindrical bodies or circularly wound cylindrical bodies in a continuous process where the sheet material, in either discrete sheet form or in continuous webs is continuously supplied to a forming mandrel and with completed cylindrical bodies continuously being sequentially delivered from the other end of the forming mandrel.
To achieve this end, the present invention includes an array of endless belts disposed along the length of the mandrel and which are arranged by separate sets of guide means to contact a portion of the periphery of the forming mandrel in a spiral path but which leave a gap to permit the continuous feeding of the discrete sheet material to the forming mandrel. Further, the mandrel and belts are rotated at predetermined relative speeds to assure accurate formation of the cylindrical body as well as transport of the formed body along the mandrel to the discharge end. With this invention, cylindrical bodies such as are used in the container industry which are made of composite material such as plastic films, foil and/or paper can also be formed into cylindrical bodies with either a circular wrap or a spiral wrap for the material constituting the body.
As has long been recognized, presently available spiral winding machines and their products suffer from a number of disadvantages. Regarding the machines, a very large number of variables must be controlled to produce uniform containers at production rates that have, in the past, been acceptable. Many of these variables, which number five to approximately seventy-five are described in an article entitled "Operating Variables in Spiral Winding: Theoretical Interrelationship and Significance" by Michael Harvey, TAPPI, Vol. 53, August 1970, p. 1521-24. The control of so many variables has inevitably limited the productive capacity of such machines thus contributing to the cost of the container bodies produced and rendering them less competitive in the container market.
In addition, the prior art spiral winding machines required the cutting of the resulting tube to provide the discrete container bodies as well as the extensive application of a wet adhesive to the sheet material in the formation process. As a consequence, use of such machines has been restricted since the dust and debris from the cutting and adhesive application operations generally precluded use of these type of machines in food plants. Moreover, the containers produced often must undergo additional cleaning operations before their introduction into a food filling line.
While spiral wound paperboard containers are economically advantageous for some products, it has been recognized that the decreased resistance to axial compression inherent in such containers renders them unsuitable for a number of the products. With circular or convolute containers, the sheet fibers can be aligned to extend generally perpendicular to the ends of the container body thus affording much greater resistance to axial compression. Conversely, this feature will enable a manufacturer to use a lesser thickness in the sheet material thereby resulting in a reduction in the cost of the container. However, machines to produce circularly as coposed to spirally wound bodies have not provided the productive speeds required to compete with other types of container materials or with spirally wound bodies.
With the apparatus and method of the present invention several of the control factors inherent in present methods of spiral winding sheet material are significantly reduced or eliminated while providing improved methods of winding capable of higher production speeds and improved control over the quality of the finished product. In addition, where the sheet material is fed transverse to the axis of the forming mandrel, significantly higher production speeds are achieved. The sheet material itself can be prepared in advance of being formed into a cylindrical body such as by the prior inclusion of liner material, label, printing, advertising and the like.
From the following description, it will be seen that the apparatus and method of the present invention will provide a rigid, convolute, gas-tight container which can be assembled at high speed from a blank of coated paperboard and where the apparatus can be easily and economically installed and operated by a filler due to the efficiency of the apparatus. With such an arrangement, the composite can manufacturing can be integrated into a filling line. Thus, the user of the apparatus will be able to form, fill and seal a container in an in line process thus resulting in substantial production savings without sacrificing production speeds, container integrity or appearance.